Run a lot, and do lots of push ups and sit ups, or start going to a gym. I'd say depends on what you want to do in the military? If you like the ocean or idea of being on a ship then the Navy is a good choice. You can be just about anything in the Navy but i guess same goes for the other branches. And in the Navy you get to travel a lot, but it is very full right now and hard to get in unless get a really high score on your ASVAB test. The Army or Marines you would have a very good chance of going to Iraq or Afghanistan.